1. Field of the Invention
This invention relates to an information record apparatus for performing power calibration when recording information on an optical information record medium such as a write-once optical disk or a rewritable optical disk, for example, a power calibration method at the information recording time, and an optical information record medium recording information to perform power calibration.
2. Description of the Related Art
In recent years, in addition to read-only CD (compact disk) and DVD (digital video disk or digital versatile disk), write-once (recordable) CD and DVD, rewritable CD and DVD, MD (mini disk), and the like have been developed for increasing the number of variations of the optical information record media.
In write-once (recordable) CD and DVD, which will be hereinafter collectively called write-once optical disk, write laser light is applied to a record film of an organic coloring matter material for forming circular or elliptic record pits, thereby irreversibly recording information. In rewritable CD and DVD, which will be hereinafter collectively called rewritable optical disk, write laser light is applied to a phase change film for repeating crystallization and rendering amorphous, thereby reversibly recording information as circular or elliptic record pits. In MD, magneto-optical recording is performed.
To form an appropriate circular or elliptic record pit defined on the specification on write-once optical disk and rewritable optical disk, write laser light is controlled by light pulse strategy.
In the light pulse strategy, the form of a light pulse relative to the record mark length is adjusted, whereby laser light emitted from a semiconductor laser is optimized, and record pits of an appropriate form are formed by the optimized laser light, so that a high-quality reproduction signal with occurrence of jitter, etc., suppressed can be provided when information is reproduced.
Power calibration to previously adjust the emission power of the semiconductor laser is executed before essential information recording is performed based on the light pulse strategy.
In the power calibration, record pits are formed in a power calibration area provided at the inner radius of an optical disk and the emission power of the semiconductor laser is optimized based on the waveform provided, for example, by AC coupling a detection signal, called HF signal, provided by optically reading the record pits formed (namely, written for a try) in the power calibration area.
That is, as with the case where normal information reading is executed, reflected light from the power calibration area in which the recordpits are formed is detected by a photo detector and outputs of the photo detector are combined, whereby the HF signal is generated. This means that the HF signal is a signal before equalizing to generate an RF signal, etc., is performed.
As the HF signal is thus generated, an eye pattern of the HF signal is provided. If the waveform is AC-coupled, top peak level a1 of the waveform indicates the potential difference between the potential indicating the strength of reflected light from a land where no record pit is formed and the potential of AC ground GND and bottom peak level a2 indicates the potential difference between the potential indicating the strength of reflected light from a record pit and the potential of AC ground GND, as shown in FIG. 12A.
The ratio between the peak-to-peak value of the HF signal (a1+a2) and the difference between the levels (a1xe2x88x92a2), which will be hereinafter referred to as xcex2 value, is found as shown in the following expression (1), and, for example, when xcex2 value=0 is adopted as the target of the power calibration, if the xcex2 value becomes almost 0, it is determined that the emission power P of the semiconductor laser is equal to target power Pw; if the waveform provided by AC coupling the HF signal becomes the waveform shown in FIG. 12B and the xcex2 value becomes a negative value, it is determined that the emission power P of the semiconductor laser is smaller than the target power Pw; and if the waveform provided by AC coupling the HF signal becomes the waveform shown in FIG. 12C and the xcex2 value becomes a positive value, it is determined that the emission power P of the semiconductor laser is larger than the target power Pw. The emission power P of the semiconductor laser is adjusted so as to become equal to the target power Pw based on each determination result.
xcex2=(a1xe2x88x92a2)/(a1+a2)xe2x80x83xe2x80x83(1) 
A method of determining whether or not the emission power P of the semiconductor laser reaches the target power Pw by examining asymmetry of the HF signal itself produced in response to the size and form of a recordpit formed in the power calibration area is also devised.
In the method of examining asymmetry, as shown in FIG. 13, top peak level A1 of the HF signal corresponding to the strength of reflected light from a land where no record pit is formed, bottom peak level A2 corresponding to the strength of reflected light from a large record pit, top peak level B1 corresponding to the strength of reflected light from a land between small recordpits, and bottompeak level B2 corresponding to the strength of reflected light from a small record pit are detected and the detected levels A1, A2, B1, and B2 are applied to the following expression (2), thereby finding the value of asymmetry, which will be hereinafter referred to as a value:
xcex1={(A1+A2)xe2x88x92(B1+B2)}/{2xc3x97(A1xe2x88x92A2)}xe2x80x83xe2x80x83(2) 
For example, when xcex1 value=0 is adopted as the target of the power calibration, if the a value becomes 0, it is determined that the emission power P of the semiconductor laser is equal to the target power Pw, and if the a value becomes unequal to 0, it is determined that the emission power P is not equal to the target power Pw, and the supply current to the semiconductor laser is controlled so that the emission power P becomes equal to the target power Pw.
When a pit is recorded and formed on an optical disk, the specification of modulation depth M found according to the following expression (3) must also be satisfied:
M=(A1xe2x88x92A2)/A1xe2x80x83xe2x80x83(3) 
However, the xcex2 value and the a value fluctuate depending on the type difference between optical disks, the pulse strategy, the characteristic variations, etc., of the optical systems and electronic elements contained in pickups and thus, if the emission power of the semiconductor laser is previously adjusted based on the xcex2 value and the a value by the power calibration described above, the modulation depth may not be provided and when record pits are formed at the essential information recording time and the information is reproduced, the modulation depth is degraded and jitter, etc., accompanying the degradation of the modulation depth occurs in the reproduction signal; this is a problem. That is, it may become difficult to optimize the emission power of the semiconductor laser with good accuracy as the power calibration based on the xcex2 value and the a value in the related art is executed.
It is therefore an object of the invention to provide an optical information record apparatus and an optical information record method for making it possible to overcome the above-described problems and recording and forming pits in appropriate form.
It is another object of the invention to provide an information record medium recording control information to record and form pits in appropriate form for controlling an electronic machine based on the control information.
To the ends, according to the invention, there is provided an information record apparatus for adjusting power of write light on to an optical information record medium, the information record apparatus comprising a light source for emitting the write light, a power adjustment section for adjusting the emission power of the write light, a write section for forming recordpits in the optical in formation record medium by applying write light of different powers emitted from the light source, a feature extraction section for optically reproducing the record state containing the record pits formed by applying the write light of different powers from the optical information record medium in which the record pits are formed and extracting feature information of the record state for each of the record pits formed by applying the write light of different powers based on the signal waveform provided by optically reproducing the record state, a detection section for detecting the modulation depth of the write light for each of the different powers based on the signal waveform provided by optically reproducing the record state, a selection section for selecting the power of the write light corresponding to the modulation depth of a larger value than a predetermined threshold value, of the modulation depths detected by the detection section, and a determination section for selecting the feature information corresponding to the power of the light write selected by the selection section from among the feature information extracted by the feature extraction section and determining that the power of the write light corresponding to the feature information closest to target feature information of a predetermined record state, of the selected feature information is appropriate write light power, characterized in that the power adjustment section adjusts the emission power of the light source based on the write light power determined to be appropriate bathe determination section.
According to the information record apparatus having the configuration, each actually provided modulation depth is compared with the predetermined threshold value and the emission power (write light power) corresponding to the modulation depth of a larger value than the modulation depth and corresponding to the feature information closest to the target feature information is determined appropriate write light power, whereby power calibration is conducted.
According to the invention, there is provided an information record apparatus for adjusting power of write light onto an optical information record medium, the information record apparatus comprising a light source for emitting the write light, a power adjustment section for adjusting the emission power of the write light, a write section for forming record pits in the optical information record medium by applying write light of different powers emitted from the light source, a feature extraction section for optically reproducing the record state containing the record pits formed by applying the write light of different powers from the optical information record medium in which the record pits are formed and extracting feature information of the record state for each of the record pits formed by applying the write light of different powers based on the signal waveform provided by optically reproducing the record state, a detection section for detecting the modulation depth of the write light for each of the different powers based on the signal waveform provided by optically reproducing the record state, a selection section for selecting the power of the write light corresponding to the feature information in a predetermined range, of the feature information extracted by the feature extraction section, and a determination section for determining that the power of the write light, of the powers of the write light selected by the selection section, corresponding to the modulation depth of the largest value, of the modulation depths detected by the detection section is appropriate write light power, characterized in that the power adjustment section adjusts the emission power of the light source based on the write light power determined to be appropriate by the determination section.
According to the information record apparatus having the configuration, the emission power (write light power) corresponding to the feature information in the predetermined range, of actually provided feature information and corresponding to the modulation depth of the largest value, of the emission power is determined appropriate write light power, whereby power calibration is conducted.
According to the invention, there is provided an information record method for adjusting power of write light onto an optical information record medium, the information record method comprising the steps of forming record pits in the optical information record medium by applying write light of different powers emitted from a light source, optically reproducing the record state containing the record pits formed by applying the write light of different powers from the optical information record medium in which the record pits are formed and extracting feature information of the record state for each of the recordpits formed by applying the write light of different powers based on the signal waveform provided by optically reproducing the record state, detecting the modulation depth of the write light for each of the different powers based on the signal wave form provided by optically reproducing the record state, selecting the power of the write light corresponding to the modulation depth of a larger value than a predetermined threshold value, of the detected modulation depths, selecting the feature information corresponding to the selected write light power from among the extracted feature information and determining that the power of the write light corresponding to the feature information closest to target feature information of a predetermined record state, of the selected feature information is appropriate write light power, and adjusting the emission power of the light source based on the write light power determined to be appropriate.
According to the information record method, each actually provided modulation depth is compared with the predetermined threshold value and the emission power (write light power) corresponding to the modulation depth of a larger value than the modulation depth and corresponding to the feature information closest to the target feature information is determined appropriate write light power, whereby power calibration is conducted.
According to the invention, there is provided an information record method for adjusting power of write light onto an optical information record medium, the information record method comprising the steps of forming record pits in the optical information record medium by applying write light of different powers emitted from a light source, optically reproducing the record state containing the record pits formed by applying the write light of different powers from the optical information record medium in which the record pits are formed and extracting feature information of the record state for each of the recordpits formed by applying the write light of different powers based on the signal waveform provided by optically reproducing the record state, detecting the modulation depth of the write light for each of the different powers based on the signal wave form provided by optically reproducing the record state, selecting the power of the write light corresponding to the feature information in a predetermined range, of the extracted feature information, determining that the power of the write light, of the selected write light powers, corresponding to the modulation depth of the largest value, of the detected modulation depths is appropriate write light power, and adjusting the emission power of the light source based on the write light power determined to be appropriate.
According to the information record method, the emission power (write light power) corresponding to the feature information in the predetermined range, of actually provided feature information and corresponding to the modulation depth of the largest value, of the emission power is determined appropriate write light power, whereby power calibration is conducted.
According to the invention, there is provided an information record medium recording control information for controlling an information record apparatus for recording information by applying write light emitted from a light source to an optical information record medium, the control information for adjusting power of the write light, the control information for controlling the information record apparatus, thereby emitting write light of different powers from the light source for forming record pits in the optical information record medium, and optically reproducing the record state containing the record pits formed by applying the write light of different powers from the optical information record medium in which the record pits are formed, extracting feature information of the record state for each of the record pits formed by applying the write light of different powers based on the signal waveform provided by optically reproducing the record state, detecting the modulation depth of the write light for each of the different powers based on the signal waveform provided by optically reproducing the record state, selecting the power of the write light corresponding to the modulation depth of a larger value than a predetermined threshold value, of the detected modulation depths, selecting the feature information corresponding to the selected write light power from among the extracted feature information and determining that the power of the write light corresponding to the feature information closest to target feature information of a predetermined record state, of the selected feature information is appropriate write light power, and adjusting the emission power of the light source based on the write light power determined to be appropriate.
According to the information record medium, if the recorded control information is executed in an electronic machine such as a personal computer, it is made possible to emulate the function of the information record apparatus implemented as hardware.
According to the invention, there is provided an information record medium recording control information for controlling an information record apparatus for recording information by applying write light emitted from a light source to an optical information record medium, the control information for adjusting power of the write light, the control information for controlling the information record apparatus, thereby emitting write light of different powers from the light source for forming recordpits in the optical information record medium, and optically reproducing the record state containing the record pits formed by applying the write light of different powers from the optical information record medium in which the record pits are formed, extracting feature information of the record state for each of the record pits formed by applying the write light of different powers based on the signal waveform provided by optically reproducing the record state, detecting the modulation depth of the write light for each of the different powers based on the signal waveform provided by optically reproducing the record state, selecting the power of the write light corresponding to the feature information in a predetermined range, of the extracted feature information, determining that the power of the write light, of the selected write light powers, corresponding to the modulation depth of the largest value, of the detected modulation depths is appropriate write light power, and adjusting the emission power of the light source based on the write light power determined to be appropriate.
Also according to the information record medium, if the recorded control information is executed in an electronic machine such as a personal computer, it is made possible to emulate the function of the information record apparatus implemented as hardware.